The Democrat leads Republican rival Connie Mack by only three points, 47 percent to 44 percent, in Florida's bellwether I-4 corridor, according to a new Tampa Bay Times/Bay News 9 poll.

Mack — who is within the poll's margin of error — is gaining on the strength of Mitt Romney in Florida, the unpopularity of President Barack Obama's policies and Nelson's struggles to close the deal despite decades in public office.

But it may not be enough for Mack, said Brad Coker of Mason-Dixon Polling & Research, which conducted the poll. "At the end of the day, if Nelson hangs on, I think it's going to be more about Mack losing it than Nelson winning," Coker said.

The I-4 corridor runs from Tampa Bay through Central Florida and is heavily concentrated with swing voters. Thus, it's a good measure of how the statewide vote might go. Nelson, who lives in Orlando, is losing by 1 percentage point in Central Florida, which tends to lean more Republican than Tampa Bay, where Nelson has a 7 point advantage.

The telephone survey of 625 registered Florida voters — all likely to vote in the November election — was conducted Oct. 22-24 for the Tampa Bay Times, Bay News 9 and Central Florida News 13. The poll, which included respondents using land-lines and cell phones, was conducted by Mason-Dixon, a nonpartisan, Jacksonville-based company. The margin of error is plus or minus 4 percentage points.

Nelson once had a commanding lead in the race but that has tightened in recent weeks, corresponding with a surging Romney in Florida. Mack, a congressman from Fort Myers, has hitched his campaign to Romney and coattails appear to be developing. In a statewide Times poll earlier this month, Nelson lead by 5 points, down three points from September.

That is similar for Senate races in other states and while the Nelson seat has never factored much in Republican hopes of regaining control the Senate, improving signs in Florida give a glint of hope.

Nelson has a 41 percent favorable rating and 35 percent unfavorable rating — weak numbers for a two-term incumbent, who has also served in the U.S. House and on the state level. Mack has a lower favorable rating 31 percent, but his unfavorable rating is 34 percent.

Ominously for Nelson, 54 percent of voters said his performance on protecting the space program was fair or poor. Nelson once traveled into space and had long been associated with the issue. But NASA has a diminished presence in Florida due to budget cuts and shifting priorities.

Mack has his own problems.

Nelson has blistered him in TV ads for missing dozens of votes in the past year to campaign back in Florida. Half of the voters said Mack's attendance record made them less likely to support him.

Not Steve Schuler of Clearwater. He said he wasn't concerned about Mack missing work. "To me, I'd rather Sen. Bill Nelson doesn't show up for work. Sometimes I think it's a good thing when politicians don't show up."

He also doesn't mind Mack's past history of bar fights and other scrapes — issues Nelson has highlighted in ads. "I don't mind an aggressive personality, that's a good thing in a leadership position. You've got to be aggressive as long as it's controlled."

Schuler, 63, who owns a pet shop, said he voted for Nelson when he was a member of the U.S. House but now aligns with the Republican Party and its focus on less regulation and lower taxes.

Nelson has long been risk-averse and kept his focus on Florida matters, no matter how small. It could be a saving grace, with 47 percent saying they trust Nelson to look out for Florida's interests versus the 40 percent who said Mack would.

"When I needed Bill Nelson he was there for us, and I respect him," said Ellen Miller, 65, of Ocala, an independent voter who said Nelson helped her and her husband navigate a VA loan. "He's a nice person who's very knowledgeable and I trust him."

Patricia Ritter, 52, of Dunedin and a registered Democrat, said she respected Nelson backing up Obama. "It shows good character. I know a lot of people backed away from health care because they were afraid. You can't have a perfect candidate, but I think you're definitely going to get a better candidate in Nelson over Mack."

Fortunately, perhaps, for Nelson there are other candidates on the ballot, independents Chris Borgia and Bill Gaylor. The polls showed 2 percent of voters prefer someone other than Nelson or Mack. That could be the edge Nelson needs.